After falling to historic lows in the early 2000s, rates of sexually transmitted diseases (STDs) are soaring to record levels. Nearly 2.3 million cases of chlamydia, gonorrhea and syphilis were reported to the U.S. Centers for Disease Control and Prevention in 2017. Experts attribute the rise to a variety of causes, including cuts in federal funding for prevention programs, a drop in condom use and the popularity of dating apps, which some health officials believe has led to an increase in unprotected sex. STD rates are highest among young people and men who have sex with other men. In addition, rates among blacks and Hispanics are higher than among whites and can reflect disparities in income, education status and access to health care. Meanwhile, researchers are seeking ways to make STD testing faster and easier. And some doctors are prescribing medicine for the sexual partners of infected patients sight unseen.

Health education teacher Leticia Jenkins talks with ninth-grade students at James Monroe High School in North Hills, Calif., about sexually transmitted diseases (STDs) in February 2018. Between 2012 and 2017, California saw a 45 percent rise in chlamydia, gonorrhea and syphilis, and the United States continues to confront a flood of new STD cases. (AFP/Getty Images/Frederic J. Brown)